Mineral ID Chart Metallic (Luster) Minerals, H=hardness, SC=Specific Gravity Mineral H SG Streak Color Form Cleavage/Fracture Diagnostic properties Pyrite FeS2 6-6.5 5 Dark grey Cubes or octahedrons Brittle. No cleavage Magnetite Fe3O4 Chalcopyrite CuFeS2 Hematite Fe2O3 6 5.2 Dark grey Octahedrons No cleavage 3.5-4 4.2 1.5-6 2.1-2.6 GreenishBlack Red to red-brown Often massive, tetragonal system Thin tabular crystals or shapeless masses. Indistinct cleavage and uneven Fracture No cleavage Galena PbS 2.5 7.6 Graphite C 1 2.1-2.3 Brass yellow; tarnishes brown. Silvery grey to black. Tarnishes grey. Opaque. Brass yellow and tarnishes to peacock blue-purple Silvery grey, black, or brick red. Luster can be nonmetallic. Silvery grey. Tarnishes dull grey. Silver grey to black Cubes and octahedrons Flakes, short hexagonal prisms, and masses. Brittle. 3 good cleavage planes (cubes). 1 excellent cleavage plane. Cubic form, brassy color, and SG=5. Attracted to a magnet. SG=5.2. No cleavage. Greenish-Black Streak, peacock colors on brass Red streak. Metallic + nonmetallic. Earthy red. SG=8! Silver cubes (form and cleavage). Dark grey. H=1. Greasy. Dark grey streak. Grey to dark grey Dark-grey Note: All the minerals above have a metallic luster. Massive means lacking a defined form. Non-metallic minerals (listed in decreasing hardness) Review mineral formula to connect to family! H=Hardness; SG = specific gravity Mineral H SG Streak Color and/or Luster Form Cleavage/Fracture Diagnostic properties Corundum Al2O3 9 4 White Gray, blue, pink, brown. Glassy or dull. Translucent to opaque. No cleavage H=9. Barrel-shaped, flat-end hexagons. 3.54.3 White Red, black, or brown; can be yellow, green, pink. Glassy. Translucent. Hexagonal prisms with striated, flat ends. Barrel shaped Dodecahedrons (12sided polygons) Garnet X3Y2(SiO4)3 where X and Y are combinations of Ca, Mg, Fe, Al 7 No cleavage. Brittle. Conchoidal fracture. 7 3.33.4 White Pale or dark olive green to yellow or brown. Glassy. Transparent. Quartz SiO2 7 2.7 White Colorless, white, or gray; can occur in all colors. Glassy and/or greasy. Epidote Ca2(Al,Fe)3Si3O12(OH) 6-7 3.33.6 White Green (with yellow or brown tinge). Translucent to opaque. Glassy. Dodecahedron form, red (sometimes), glassy, conchoidal fracture, H=7. Green, conchoidal fracture, glassy, H=7. Usually granular. Not a hexagonal crystal. Glassy, conchoidal fracture, H=7. Hex. prism with pointed end. H=7. Green. Striated crystal faces. Massive Olivine (Mg,Fe)2SiO4 Short prisms (usually too small to see). Massive; or hexagonal prisms that end in a point. Striated prisms, or massive. Conchoidal fracture.Brittle. Conchoidal fracture. One good, one poor and rarely visible. Mineral H SG Streak Color and/or Luster Form Cleavage/Fracture Diagnostic properties Kyanite Al2SiO5 4-7 3.6 White Patchy blue; can be green, white, gray. Glassy, pearly. Translucent. Green (can be white to pink as well). Glassy. Opaque. Bladed masses. Flexible crystals, bent or twisted Long, thin columnar or needle-like crystals. One perfect cleavage plane parallel to blades. Blue, flexible blades. Amphibole family: Actinolite Ca2(Mg,Fe)5Si8O22(OH)2 6 33.5 White, green Plagioclase Feldspar family: Anorthite and Labradorite CaAl2Si2O8 to Oligoclase and Albite NaAlSi3O8 Potassium Feldspar family: Orthoclase and Microcline KAlSi3O8 6 2.62.8 White 6 2.52.6 White Pyroxene family: Augite Ca(Mg,Fe,Al)(Al,Si)O6 5.56 3.23.5 White, pale grey Green to black; opaque. Short, 8-sided prisms (if visible). 2 good cleavage planes at nearly right angles. Amphibole family: Hornblende Ca(Mg,Fe)4Al(Si7Al)O22(OH) 2 5.5 33.3 Greygreen, white Dark green to black. Opaque. Long, perfect prisms. 2 cleavages planes. Angles: 60° and 120°. Brittle. Splintery fracture. Limonite Goethite (FeO(OH) FeO(OH)*nH20 Apatite Ca5(PO4)3(F,Cl,OH) Fluorite CaF2 45.5 2.74.3 Yellow brown Light brown to brown, Dull earthy luster. Amorphous, can be psuedomorph No cleavage 5 3.1 White Color varied, vitreous hexagonal Conchoidal frac. Softer than quartz 4 3.2 White Color varied, vitreous Octahedral 4 excellent cleavage directions. Gives crystal shape triangular faces. Brittle. Fluorescent, 4 directions of cleavage. Triangular faces. Colorless, white, gray, or black; can have iridescent play of color from within. Translucent to opaque. Pink. Or white, orange, brown, gray, green. Translucent to opaque. Tabular crystals or thin needles Tabular crystals Green, thin needles. 2 good planes. Angles: 56° and 124°. 2 good cleavage planes at nearly right angles. 2 good cleavage planes at nearly right angles. Twinning. 2 cleavages at 90°. H = 6. Subparallel exsolution lamellae. 2 cleavages at 90°. Pink or white color. H = 6. No twinning H=5.5. Dark green or black. 2 cleavages at 90°. (Looks like HB.) H=5.5. Dark green or black. 2 cleavages at 60°& 120°. Splintery fracture. Long prisms. Dull, earthy and yellow streak. Mineral H SG Streak Color and/or Luster Form Cleavage/Fracture Diagnostic properties Calcite CaCO3 3 2.7 White Usually colorless, white, or yellow, can be green, brown, or pink. Glassy. Opaque to transparent. Rhombohedrons. 3 excellent cleavage planes. Angles: < 90° and > 90°. 2.73.1 Greybrown Black, green-black, brown-black. Transparent to opaque. Short tablets. Like a tablet of paper. 1 excellent cleavage – splits easily into thin, flexible sheets. 2-2.5 2.73 White Serpentine Mg6Si4O10(OH)8 2-5 2.22.6 White Colorless, yellow, brown, or red-brown. Transparent to opaque. Pale or dark green, yellow, grey. Opaque. Dull or silky. Short tablets. Like a tablet of paper. Smooth, rounded masses. 1 excellent cleavage – splits easily into thin, flexible sheets No cleavage. Chlorite (Mg,Fe)5(Al,Fe)2Si3O10(OH)8 2-2.5 2-3 White Dark or bright green. Opaque. Halite NaCl 2.5 2.12.6 White Gypsum CaSO4*2(H20) 2 2.3 White 1 excellent cleavage – splits easily into thin sheets. Brittle. 3 excellent cleavage planes: cubes. 1 good cleavage plane. Bauxite gibbsite, Al(OH)3 Talc Mg3Si4O10(OH)2 1-3 22.5 2.72.8 White Colorless, white, yellow, blue, brown, or red. Glassy. Colorless, white, or grey. Translucent to transparent. white, gray, yellow, red, dull to earthy luster White, grey, pale green, or brown. Opaque. Greasy or silky luster. Short tablets. Like a tablet of paper. Cubes. Bubbles in HCL. Double refraction (2 images visible through clear sample). Rhombs, 3 cleavage planes (not 90°), H=3. 1 flexible cleavage plane (sheet), dark colored; brown streak. 1 flexible cleavage plane (sheet), light colored; white streak. Mottled green color. Smooth, curved surfaces. No cleavage. H>2. Green, nonflexible sheets. Very small flakes. Salty taste. H=2.5. Cubic form and cleavage. H=2. 1 cleavage plane. Translucent. pisolitic structure, color Feels greasy or soapy. H=1. Opaque. Not metallic. Mica family: Biotite K(Mg,Fe)3AlSi3O10(OH)2 2.5-3 Mica family: Muscovite KAl3Si3O10(OH)2 1 White Tabular, prisms, blades, or needles. Pisolitic structure Shapeless masses (if no cleavage visible) or tabular. No cleavage 1 poor cleavage plane (may not be visible). Note: Striations and splintery fracture are very similar. They both look like ridges; you can feel the texture of both. Splintery fracture results from breakage (similar to breaking wood and getting splinters); striations usually results from crystal growth. Twinning is more lines, less ridges. It cannot be felt – only seen.